mirror of https://github.com/M66B/FairEmail.git
127 lines
4.7 KiB
Kotlin
127 lines
4.7 KiB
Kotlin
/*
|
|
* Copyright 2018 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
package androidx.room
|
|
|
|
import android.annotation.SuppressLint
|
|
import androidx.arch.core.executor.ArchTaskExecutor
|
|
import androidx.lifecycle.LiveData
|
|
import java.lang.Exception
|
|
import java.lang.RuntimeException
|
|
import java.util.concurrent.Callable
|
|
import java.util.concurrent.Executor
|
|
import java.util.concurrent.atomic.AtomicBoolean
|
|
|
|
/**
|
|
* A LiveData implementation that closely works with [InvalidationTracker] to implement
|
|
* database drive [androidx.lifecycle.LiveData] queries that are strongly hold as long
|
|
* as they are active.
|
|
*
|
|
* We need this extra handling for [androidx.lifecycle.LiveData] because when they are
|
|
* observed forever, there is no [androidx.lifecycle.Lifecycle] that will keep them in
|
|
* memory but they should stay. We cannot add-remove observer in [LiveData.onActive],
|
|
* [LiveData.onInactive] because that would mean missing changes in between or doing an
|
|
* extra query on every UI rotation.
|
|
*
|
|
* This [LiveData] keeps a weak observer to the [InvalidationTracker] but it is hold
|
|
* strongly by the [InvalidationTracker] as long as it is active.
|
|
*/
|
|
@SuppressLint("RestrictedApi")
|
|
internal class RoomTrackingLiveData<T> (
|
|
val database: RoomDatabase,
|
|
private val container: InvalidationLiveDataContainer,
|
|
val inTransaction: Boolean,
|
|
val computeFunction: Callable<T?>,
|
|
tableNames: Array<out String>
|
|
) : LiveData<T>() {
|
|
val observer: InvalidationTracker.Observer = object : InvalidationTracker.Observer(tableNames) {
|
|
override fun onInvalidated(tables: Set<String>) {
|
|
ArchTaskExecutor.getInstance().executeOnMainThread(invalidationRunnable)
|
|
}
|
|
}
|
|
val invalid = AtomicBoolean(true)
|
|
val computing = AtomicBoolean(false)
|
|
val registeredObserver = AtomicBoolean(false)
|
|
val refreshRunnable = Runnable {
|
|
if (registeredObserver.compareAndSet(false, true)) {
|
|
database.invalidationTracker.addWeakObserver(observer)
|
|
}
|
|
var computed: Boolean
|
|
do {
|
|
computed = false
|
|
// compute can happen only in 1 thread but no reason to lock others.
|
|
if (computing.compareAndSet(false, true)) {
|
|
// as long as it is invalid, keep computing.
|
|
try {
|
|
var value: T? = null
|
|
while (invalid.compareAndSet(true, false)) {
|
|
computed = true
|
|
try {
|
|
value = computeFunction.call()
|
|
} catch (e: Exception) {
|
|
throw RuntimeException(
|
|
"Exception while computing database live data.",
|
|
e
|
|
)
|
|
}
|
|
}
|
|
if (computed) {
|
|
postValue(value)
|
|
}
|
|
} finally {
|
|
// release compute lock
|
|
computing.set(false)
|
|
}
|
|
}
|
|
// check invalid after releasing compute lock to avoid the following scenario.
|
|
// Thread A runs compute()
|
|
// Thread A checks invalid, it is false
|
|
// Main thread sets invalid to true
|
|
// Thread B runs, fails to acquire compute lock and skips
|
|
// Thread A releases compute lock
|
|
// We've left invalid in set state. The check below recovers.
|
|
} while (computed && invalid.get())
|
|
}
|
|
|
|
val invalidationRunnable = Runnable {
|
|
val isActive = hasActiveObservers()
|
|
if (invalid.compareAndSet(false, true)) {
|
|
if (isActive) {
|
|
queryExecutor.execute(refreshRunnable)
|
|
}
|
|
}
|
|
}
|
|
|
|
@Suppress("UNCHECKED_CAST")
|
|
override fun onActive() {
|
|
super.onActive()
|
|
container.onActive(this as LiveData<Any>)
|
|
queryExecutor.execute(refreshRunnable)
|
|
}
|
|
|
|
@Suppress("UNCHECKED_CAST")
|
|
override fun onInactive() {
|
|
super.onInactive()
|
|
container.onInactive(this as LiveData<Any>)
|
|
}
|
|
|
|
val queryExecutor: Executor
|
|
get() = if (inTransaction) {
|
|
database.transactionExecutor
|
|
} else {
|
|
database.queryExecutor
|
|
}
|
|
}
|